I have to just say that I can't think of anything else except that advertising sales just does not scale. You may point to Google. But they are what in UK fin

I have to just say that I can't think of anything else except that advertising sales just does not scale. You may point to Google. But they are what in UK financial regulation speak, is called a Systematic Internaliser. They operate a two way market without substantial open interest not provided except internally from client order flows executed according to their own instruction interpretations.